1. Field of the Invention
The present invention relates to a bearing arrangement of an external-axial rotary piston blower for gaseous media with a housing which consists of a casing with an internal raceway surface and two side parts and a piston rotating in the housing to form working or operating chambers therewith, whereby the shafts of these pistons have ball bearings with lip seals for sealing-off of the gas pressure in the working or operating chambers as well as having gear wheels externally of these bearings.
2. Description of the Prior Art
Such blowers can be those of so-called Rootstype of construction or half-roller i.e. semi-cylinder blower type of construction respectively quarter-roller i.e. quarter-cylinder-blower type of construction, which have two pistons identical among each other operating in meshing, complementary or dovetail engagement rotating oppositely with a transmission ratio 1:1. Such blowers are employed and utilized especially as chargers for internal combustion engines with air as a working or operating medium.
With such machines, which for economical and efficiency reasons must have a simple, straightforward construction as inexpensive as possible in mass production, the working chambers are sealed-off only by sealing gaps with respect to each other and relative to shaft passages through the side parts of the housing. The changing impingement, impacting or stress of the working chamber with over pressure and under pressure leads to a pulsation of the working medium that subjects the ball bearings to flow impact or shocks changing in rapid sequence as to the direction thereof. The lip flap or face seals of the particular respective ball bearing close during over pressure in the adjoining working chamber and in the gap spaces connecting with the ball bearings. There cannot be avoided however that an over pressure builds up via an incomplete sealing-off of the bearings in the cover space or chamber receiving the gear wheels, which over pressure opens the lip flap or face seals of the ball bearings after the suction cycle located in the working or operating chambers and thereby pressing the transmission lubricant into these working chambers. Consequently transmission lubricant is lost not only uncontrolled but rather transmission lubricant also reaches and comes into the operating medium which is to be free of oil.
The lip flap or face seals lift likewise during under pressure in the working or operating chambers respectively in the gap spaces or chambers connecting them with the ball bearings, whereby then in essence the bearing grease or lubricant is suctioned away from the permanently lubricated ball bearings so that these ball bearings very soon suffer damage.
In so doing there is to be noted that the suctioning-off of the transmission grease or lubricant occurs then when under pressure occurs or arises only upon the side of the bearing toward the working or operating chambers, while the lubricant or oil pressed through the ball bearings during over pressure in the cover chamber or space can prevent this suctioning-off. Accordingly, measures are not sufficient or adequate which prevent the occurrence of such an under pressure upon the working or operating chamber side of the ball bearings. On the other hand, also the arrangement of an over pressure valve at the cover space or chamber is not adequate or sufficient, since the lubricant or oil creeping, leaking or flowing in the ball bearings already is pressed through these ball bearings before the over pressure valve responds or reacts.